Uncovering the Impact of Anthropogenic Carbon Dioxide on Coastal Oceans: A Study on the U.S. East Coast

The study conducted by researchers from the University of Delaware, led by Xinyu Li and supervised by Wei-Jun Cai, sheds light on the sources and accumulation of anthropogenic carbon in the U.S. East Coast. The researchers analyzed a high-quality carbonate dataset from five research cruises conducted between 1996 and 2018 along the Mid-Atlantic Bight, a coastal region stretching from Massachusetts to North Carolina.

Surface water, the top 200 meters of the ocean, showed the highest increase in anthropogenic carbon dioxide due to direct contact with the atmosphere, leading to greater absorption of atmospheric CO2. The study revealed a “sandwich structure” distribution of carbon dioxide, with high levels of anthropogenic carbon on the surface, low levels in the middle layers, and intermediate levels deeper down.

The researchers found that water age plays a crucial role in the accumulation of anthropogenic carbon dioxide, with newer surface water exhibiting higher levels of anthropogenic carbon dioxide compared to older water masses like the Antarctic Intermediate Water and North Atlantic Deep Water. The study also highlighted a decrease in anthropogenic carbon from offshore to nearshore waters, correlating with lower salinity.

The findings of the study have broader implications for the global carbon cycle, clarifying conflicting views from terrestrial studies. The research suggests that there is no natural transport of anthropogenic carbon from terrestrial systems to coastal waters, with the majority of anthropogenic carbon in coastal waters originating from offshore water masses and local atmospheric sources.

Overall, this study provides valuable insights into the sources and distribution of anthropogenic carbon in coastal oceans, emphasizing the importance of understanding the impact of human activities on marine ecosystems and the global carbon budget.